88355711 gastrointestinal physiology objectives answered

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Gastrointestinal Physiology

Section 1

Functions and Regulation of the GI Tract:

1. List the major organs within the GI system and overall functions of the GI system.

- GI tract: mouth, esophagus, stomach, small intestine, large intestine, rectum and anus

- Accessory glands: salivary glands, liver, gallbladder and pancreas

2. Differentiate between ingestion, digestion, absorption, metabolism, secretion, and

excretion

- Ingestion: take food into the body by swallowing or absorbing it.

- Digestion: process of breaking down food by mechanical or enzymatic action in the stomach

and intestines

- Absorption: pass into the body from the GI

- Metabolism: chemical process occurring within a body to maintain life

- Secretion: substances produces by cells or glands are moved into the GI

- Excretion: removal from the body.

3. Review histological features of the wall of the GI

tract

- Four histologically defined regions:

o Mucosa: consists of single layer epithelium

that is highly folded. The epithelium is

frequently invaginated to form tubular

exocrine glands

o Submucosa: connective tissue layer with

major blood and lymph vessels. Also has

large number of ganglion cells forming the

Meissner’s plexus

o Muscularis externa: contains major smooth

muscle (peristalsis); inner circular and

outer longitudinal

o Serosa: thin connective tissue through which the major vessels and extrinsic nerve

enter

4. Compare and contrast smooth and striated

muscle with respect to structure, excitation contraction coupling, and cellular

mechanism of contraction.

Comparison between Smooth and Straited Muscles.

- Cell bundles in SM have diverse orientations due to the lack of a discrete muscle origin and

insertion.

- Contractile filaments are arranged irregularly (no sarcomeres) – this allows force

generation over a wide range of muscle lengths (termed “length adaptation”). There are

large numbers of actin filaments attached to dense bodies and it is mainly through

interconnections of these dense bodies that the force of contraction is transmitted from cell

to cell.

- Smooth muscle contains both actin and myosin filaments. It does not contain the normal

troponin complex that is necessary in the control of skeletal muscle contraction.

- Contraction of smooth muscle requires conformational alteration of myosin head whereas

with striated muscle there is movement of the troponin-tropomyosin complex on the actin

filament.

- The Sarcoplasmic Reticulum is not organized into a T-tubule system. The caveoli which

represent invaginations of the smooth muscle membrane are analogous to T tubules in

striated muscle

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88355711 gastrointestinal physiology objectives answered